When a log is sawn, the wood contains very large amounts of water. Accordingly products made from wood materials (e.g., lumber, veneer products, wood strand products) naturally contain moisture. Companies that manufacture such products seek to reduce this initial moisture content in order to avoid problems associated with dimensional stability, durability, appearance, shipping costs, fungal damage, and other issues.
Wood products are often classified and sorted into grades indicating quality and suitability for a particular use. In the lumber industry, formal grading systems are used to maintain standards so that lumber in a given grade can be used for the same application. Lumber grading is based on many factors including density, defects, and moisture content. Formal and informal grading systems based on similar factors also exist for veneers, strands, and other wood materials. Because higher grade materials generally sell for a premium price, moisture content is an important factor, which relates to product value.
Many companies that manufacture wood products employ various drying methods (e.g., kiln drying, air drying, shed drying) to reduce moisture content of their products before sale. Although companies use controlled drying processes and various monitoring technologies, it is difficult to ensure that every wood product dried in a given process will exhibit exactly the same moisture content after drying. In a kiln drying process, for example, moisture variations can result from variable drying conditions between different kilns at the same mill or within a single kiln charge. Accordingly, there is an opportunity to capture increased wood product value from improved management of moisture content. Thus, there is a need to develop a method for identifying sources of variability within drying processes for wood products and quantifying the contribution to variability from each of the sources.